Lubricants

ABSTRACT

A lubricant composition comprises a major amount of lubricating oil and a minor amount of one or more oil-soluble dithiophosphoric acid derivatives having the general formula:   WHEREIN R3 is a mono- or di-valent aliphatic or aromatic group; X is an oxygen or sulphur atom; R4 is an alkyl group; R1 and R2 are the same or different and are alkyl, alkaryl, aryl or aralkyl groups or alkenyl and n is 0 when R3 is a monovalent group or is 1 when R3 is a divalent group. The dithiophosphoric acid derivatives, certain of which are novel compounds, function as antioxidants, load carrying and antiwear additives in the lubricant compositions.

United States Patent 1 Elliott et al.

[451 Oct. 29, 1974 LUBRICANTS [73] Assignee: Edwin Cooper & CompanyLimited, London, England [22] Filed: July 5, 1972 [2]] Appl. No.:269,205

[30] Foreign Application Priority Data July 6, 1971 Great Britain31634/71 [52] US. Cl. 252/46t7, 252/400 A [51] Int. Cl C10m l/48 [58]Field of Search 252/46.7, 400 A [56] References Cited UNITED STATESPATENTS 2,648,696 8/1953 Whetstone 260/935 2,743,235 4/1956 McDermott252/46.7 3,3l7,425 5/1967 Hasserodt et al... 252/46.7 3,446,738 5/1969Chao et al. 252/46.7 3,537,998 ll/l970 Lowe 252/46.7

Primary Examiner-Helen M. S. Sneed Attorney, Agent, or FirmBacon &Thomas [5 7 ABSTRACT A lubricant composition comprises a major amount oflubricating oil and a minor amount of one or more oilsolubledithiophosphoric acid derivatives having the general formula:

wherein R is a monoor di-valent aliphatic or aromatic group; X is anoxygen or sulphur atom; R is an alkyl group; R and R are the same ordifferent and are alkyl, alkaryl, aryl or aralkyl groups or alkenyl andn is 0 when R is a monovalent group or is 1 when R is a divalent group.

The dithiophosphoric acid derivatives, certain of v which are novelcompounds, function as antioxidants, load carrying and antiwearadditives in the lubricant compositions.

8 Claims, No Drawings LUBRICANTS This invention relates to lubricantsand in particular to lubricants containing S-carbamoyl dithiophosphates.

Many dithiophosphate compounds have been employed as additives inlubricants to reduce wear and to act as antioxidants, the most widelyused additives being the zinc salts of 0,0'-dihydrocarbyldithiophosphoric acids. These zinc salts have been widely used for manyyears and have proved to be very useful in formulating lubricants.Nevertheless, the zinc salts suffer from a number of disadvantages andin particular cannot be employed in ash-free lubricants since the zinccontent is a source of ash. Consequently efforts have been made toprepare ash-free dithiophosphoric acid derivatives which can be employedas antioxidants, load carrying and antiwear additives.

In US. Pat. No. 3,537,998 there are described certain dithiophosphoricacid derivatives useful as antioxidant, antiwear and extreme pressureadditives, which derivatives have the formula:

wherein Ar is arylene of from 6 to 12 carbon atoms and R is ahydrocarbyl group, substantially free of aliphatic unsaturation, havingfrom 12 to 30 carbon atoms.

It is desirable that dithiophosphate lubricant additives in addition topossessing antioxidant, loadcarrying and antiwear properties, should notbe unduly prone to form deposits in oil solution at the elevatedtemperatures at which internal combustion engines are normally operated.e.g., up to 130C.

The present invention provides lubricants containing ash-freedithiophosphoric acid derivatives, some of which are novel compounds,having a reduced tendency to form deposits composed of oil-insolublediisothiocyanate decomposition products.

Accordingly the present invention provides a lubricant compositioncomprising a major amount of lubricating oil and a minor amount of oneor more oilsoluble dithiophosphoric acid derivatives having the generalformula:

R 's" A wherein R is a monoor di-valent aliphatic or aromatic group; Xis an oxygen or sulphur atom; R is an alkyl group; R and R are the sameor different and are alkyl, alkaryl, aryl or aralkyl groups or alkenyland n is 0 when R is a monovalent group or is 1 when R is a divalentgroup.

The additives of the present invention may contain as a contaminant. asmall proportion of isothiocyanate decomposition products.

The groups R and R are preferably alkyl, alkaryl or aralkyl groups. andmay contain from l to 30, preferably 4 to l8, carbon atoms. The group Rmay contain from l to 30. preferably 2 to 22. more preferably 4 to l3.carbon atoms. The group R is preferably a monovalent alkyl groupcontaining from 1 to 18 carbon atoms or a di-valent aryl'group,optionally bearing one or more alkyl substituents, which contains from 6to 24 carbon atoms. a

lt will be understood that the carbon atom content of the groups R, R,R" and R will be selected so as to provide an oil-soluble compound.

The dithiophosphoric acid derivatives employed in the lubricants of thepresent invention may be prepared by reacting an isocyanate compound, asmore fully described hereinaftenwith a dithiophosphoric acid. Thedithiophosphoric acid'starting materials may be prepared by reaction of1 mole of phosphorus pentasulphide with 4 moles of an alcohol ormixtureof alcohols, a phenol or mixture of phenols or a mixture of one or morealcohols and one or more phenols in accordance with techniqueswell-known in the preparation of the zinc salts of 0,-0-dihydrocarbyldithiophosphoric acids hereinbefore described. Thus, the nature of thealcohol and/or phenol employed will determine the nature of the groups'Rand R in the additives of the present invention. Examples of alcoholswhich may be used include:

ethanol n-propanol isopropanol n-butanol isobutanol amyl alcohol,including mixed amyl alcohols mixtures of alcohols, derived from the OX0process decanol dodecanol lauryl alcohol Suitable phenols include:

p-tert-butyl phenol heptyl phenol p-nonyl phenol m-pentadecyl phenolpolyalkylene substituted phenols preferably derived from polypropylene,especially propylene tetramer, and polyisobutylenes having molecularweights up to 2,500.

Examples of suitable mixtures of alcohols and phenols include:

mixtures of isobutanol with mixed amyl alcohols isopropyl alcohol andl-methyl heptanol isopropyl alcohol and 2-ethyl hexanol isobutanol and2-ethyl hexanol amyl alcohol and p-tertiary octyl phenol Thedithiophosphoric acids prepared in the above described manner arereacted with the isocyanate compound.

The isocyanate compound which may be employed in the preparation of theadditives can be a monoisocyanate, preferably an aliphaticmono-isocyanate, of the formula:

Suitable mono-isocyanates which may be used to prepare S-carbamoyldithiophosphates which may be used in the present invention include:

methyl isocyanate ethyl isocyanate n-propyl isocyanate isopropylisocyanate n-butyl isocyanate tert-butyl isocyanate octadecyl isocyanatcallyl isocyanate phenyl isocyanate Alternatively, the isocyanatecompound can have the formula:

wherein R, R and X are as hereinbefore defined. lsocyanates of thelatter formula may be prepared by reacting one of the isocyanate groupsof a di-isocyanate with an alcohol or mercaptan.

la a further alternative preparation of the additives used in thepresent invention a dithiophosphoric acid is reacted with one of theisocyanate groups of a diisocyanate and the remaining isocyanate groupis reacted with an alcohol or mercaptan.

Suitable di-isocyanates include toluene 2,4, diisocyanate, which isparticularly preferred.

Other di-isocyanates are:

diphenyl methane di-isocyanate 3-3-dimethyl-4,4' biphenylenedi-isocyanate trimethyl hexamethylene di-isocyanate hexa methylenedi-isocyanate Compounds which may be reacted with the diisocyanateinclude:

methanol ethanol isopropanol n-butanol isobutanol amyl alcohol n-hexylalcohol Z-ethylhexanol 3,5,5-trimethyl-hexanol isodecanol n-decanoldodecanol isotridecanol mixed straight chain alcohols sold under thetrade name Alfol containing up to 22 carbon atoms, and n-dodecylmercaptan.

The temperature at which the additives of the present invention areprepared may be varied according to the preparative route chosen. Inorder to obtain the optimum antioxidant performance, load-carryingability and to minimise deposit formation at elevated temperatures it ispreferred to carry out the reaction with the dithiophosphoric acid atabout 75 80C., although temperatures of up to 100C. or as low as ambienttemperature may be employed. if desired.

Each of the reactions carried out in the preparation of the additives isconventiently carried out at atmospheric pressure. However, any or allof the reactions may be carried out, if desired, at pressures above orbelow atmospheric.

The lubricants of the present invention may contain from 0.1 topreferably from 0.5 to 5%, by weight of the dithiophosphoric acidderivatives. The lubricants may also contain other additives of the typeconventionally used in lubricants, especially ash-free additives. Suchadditives include antioxidants and antiwear additives (additional to thedithiophosphoric acid derivatives) and corrosion inhibitors, detergents,dispersants, viscosity index improvers. extreme pressure additives orany combination thereof.

Suitable additional antioxidants are phenothiazine, optionallysubstituted on one or both benzene nuclei and/or the nitrogen atom, ahindered phenol or a hindered bis-phenol or a secondary amine having twoaromatic nuclei attached to the nitrogen atom. In one aspect of theinvention the additional antioxidant is a secondary amine having twoaromatic nuclei attached to the nitrogen atom, in which one or both ofthe aromatic nuclei bear one or more alkyl groups, particularly alkylgroups containing from 4 to 12, more preferably 8 or 9, carbon atoms.Examples of such amines are monooctyl phenyl-a-naphthylamines andmono-octyl phenyl-B-naphthylamines, particularly N-p-t-octylphenyl-a-naphthylamine and N-p-t-octyl phenyl-finaphthylamine; andmono-nonyl phenyl-anaphthylamines and mono-nonyl phenyl-B-naphthylamines. Other amines are diphenylamine and monoor di-alkyldiphenylamines, particular examples being di-octyl and di-nonyldiphenylamines, especially the p-p isomers. These secondary amines maybe used in an amount of from 0.1% by weight, preferably 0.2% to 5% byweight. Other ash-free antioxidants which may be used include thetrithiopyrophosphate additives described in British Pat. No. 1,254,554,and in German Offenlegungsschrift No. 2,162,180 and copending UnitedStates application Ser. No. 252,254 filed May 11, 1972.

Suitable corrosion inhibitors include benzotriazole or a derivativethereof, an aliphatic carboxylic acid, a dicarboxylic acid, for example,dodecenyl succinic acid, mercaptobenzothiazole and benzothiazoledisulphide.

Suitable detergents include an alkaline earth metal petroleum or alkylbenzene sulphonate, carboxylate, salicylate or naphthenate, any of whichmay be overbased with an alkaline earth metal carbonate. Other suitabledetergents, which may also be overbased, include a phosphosulphurisedhydrocarbon and an alkyl phenol which has been neutralised by analkaline earth metal base.

A suitable dispersant is a long chain hydrocarbon substituted by apolyamine group attached thereto either directly or through an amide orimide link, as described in British Pat. Nos. 1,068,235 and 1,121,641.

A typical viscosity index improver which may be used in this inventionis a copolymer of a mixture of monomers, which monomers are esters ofacrylic or methacrylic acid. Other unsaturated monomers such as N- vinylpyrrolidone, diethylamino-ethyl methacrylate or fumaric acid may beincluded in the mixture to give viscosity index improvers havingdispersant properties.

In certain cases, e.g., for ease of transport, it may be desirable toprepare more concentrated solutions of the dithiophosphoric acidderivatives which can be diluted with additional lubricating oil beforebeing used. These more concentrated solutions may be oil concentrates oradditive packages, i.e., may be, respectively concentrated solutions ofone or more dithiophosphoric acid derivatives or concentrated solutionsof mixtures of one or more dithiophosphoric acid derivatives and one ormore known additives. Accordingly, in a further embodiment of theinvention there is provided an oil concentrate or additive packagecomprising from 10% to more preferably 20% to 50%, by weight of alubricating oil having dissolved therein from 90% to 30%, morepreferably to 50%, by weight of one or more of the dithiophosphoric acidderivatives, optionally together with one or more known additives.

The lubricating oil employed in the lubricants, oil concentrates andadditive packages of the present invention may be a mineral oil oflubricating viscosity of well-known type. Alternatively, a syntheticester-based oil may be used as the lubricating oil. Suitable syntheticester oils are described in British Pat. Nos. 930,136 and 1,205,177.

As hereinbefore stated certain of the dithiophosphoric acid derivativesemployed in the lubricants are novel compounds. The present inventiontherefore includes in another aspect novel dithiophosphoric acidderivatives suitable for use as lubricant additives, having the generalformula:

wherein R, R R as a di-valent group, R and X are as hereinbeforedefined.

1n yet another aspect of the present invention there is provided aprocess for the preparation of a dithiophosphoric acid derivative, whichprocess comprises reacting an isocyanate compound of the formula:

0 0 CNR3NH ll-X-R with a compound of formula:

R 0 SH to produce a dithiophosphoric acid derivative having the generalformula:

wherein R, R R as a di-valent group, R and X are as hereinbeforedefined.

Moreover the present invention further provides a process for thepreparation of a dithiophosphoric acid derivative, which processcomprises reacting a compound of the formula:

with one of the isocyanate groups of a di-isocyanate and thereafterreacting the remaining isocyanate group with an alcohol or mercaptan.

It is to be understood that the invention also includes adithiophosphoric acid derivatives when produced by either of the aboveprocesses.

The preparation of dithiophosphoric acid derivatives which may be usedin lubricants in accordance with the present invention will now beillustrated with reference to the following non-limiting examples.

EXAMPLE 1 Ethyl isocyanate (13.8g. 0.2m) was added dropwise to stirreddi-tridecyl dithiophosphoric acid (110g.

' 0.2m) over a period of about 1 hour, the temperature of the reactionmixture being maintained at -85C. After each addition an exotherm wasnoticed.

When the addition was complete the product was allowed to cool slowly,with stirring, to yield g. (97%) of a light green mobile liquid.

Analysis: 5.47 P. 11.16 S 2.16 N Theory 5.49 P. 11.32 S 2.48 N TimkenO.K. load 45 lbs.

EXAMPLE 2 Analysis 3.63 N. 3.98 P 8.1 '71 S Theory 3.58 70 N. 3.97 "/1 P8.18 7r S Timken O.K. load 60 lbs.

EXAMPLE 3 Di-isobutyl dithiophosphoric acid (250g. 1m) was added totoluene di-isocyanate (174g. 1m) from a tap funnel over a period of /4hour at 7080C. After being left for 2 hours, with stirring,2-ethylhexanol (143g. 1.1m) was added dropwise over a period of 1 hour.After a further /2 hour, stirring and heating was stopped, the productwas filtered and stripped to 120C. and 4 torr to yield 525 g. (96.3%).

Analysis: 5.67 I P 4.95 N. 11.12 S. Theory 5.67 P. 5.14 N. 11.72 7r S.Timken O.K. load 45 lbs.

EXAMPLE 4 Isobutanol (14.8g., 0.2m) was added dropwise over hour totoluene di-isocyanate (34.8g., 0.2m.), initially at 7080C., causing thetemperature to rise briefly to l 10C. 0,0-di-tridecyl dithiophosphoricacid (110.2g., 0.2m) was then added, dropwise over one hour, with thetemperature being maintained at 7080C. A further quantity of isobutanol(1.5g, 10%) was then added to ensure that there was no free isocyanatein the product, and the mixture stirred for acid one hour to yield 157g.(97.5%) of a greenish yellow liquid containing 3.97%P (theory 4.18).

Timken O.K. load 50 lbs.

EXAMPLE a. Toluene di-isocyanate 174g, 1.0m) was heated to approximately105C. and 0,0-di-isobutyl dithiophosphoric acid (250g. 1.0m) run in over/4 hour and left to react for a further 2 /4 hours at 105C.

b. To 100g. (0.24m.) of the product of (a) was added n-dodecyl mercaptan(47.5g., 0.24m) over 20 minutes at approximately 105C. After stirringfor a further /2 hour the product was cooled to yield 146g. (99%) of anolive green liquid containing 5.0%P and 16.4%S (theory 5.02% and 15.55%respectively).

EXAMPLE 6 3,5,5-Trimethyl hexanol (57.6g., 0.4m) was added to toluenedi-isocyanate (69.6g., 0.4m.) at a temperature of 70-80C. and0,0'-di-isobutyl dithiophosphoric 106g, 0.4m.) was added to the reactionproduct dropwise over a one hour period, followed by reaction for afurther 1 A hours. A yield of 223g. (95.5%) ofa dark grey/greensemi-solid containing 5.85%P (theory 5.52%) was obtained.

Timken O.K. load 27 lbs.

EXAMPLE 7 Toluene di-isocyanate (69.6g., 0.4m.) was added to tridecanol(80.0g., 0.4m.) at 7080C., and to the reaction product was added0,0'-di-isobutyl dithiophosphoric acid (l06.8g., 0.4m.) dropwise overhour. The reaction was continued with stirring for a further hour toyield 245g. (99%) of a green, slightly viscous liquid containing 5.44%P(theory 5.04%).

Timken O.K. load 30 lbs.

EXAMPLE 8 Tridecanol (40.0g., 0.2m.) was added to toluene diisocyanate(34.8g.. 0.2m.) over /2 hour at a temperature of 7080C. and the productstirred for a further V2 hour. To the product was then added0,0'-di-isobutyl dithiophosphoric acid (55.6g., 0.2m.) over /4 hourfollowed by a further 4.0g. (10%) of tridecanol and the reactioncontinued for a further one hour to yield 1 19g. (95% of an olive greenliquid containing 5.00%? (theory 5.04%

Timken O.K. load 45 lbs.

EXAMPLE 9 An 0,0-dialkyl dithiophosphoric acid was prepared by reactionof P 5 with Alfol 20-22 (a commercially available mixture of alcoholscontaining 20-22 carbon atoms). To toluene di-isocyanate (34.8g., 0.2m.)was added, in bulk. 2-ethylhexanol (26g, 0.2m.), causing an exotherm. Tothe product was added the 0,0'-di- Alfol 20-22 dithiophosphoric acid(150g.,0.2m.), after melting. causing the temperature to rise to 50C.The total addition time of the dithiophosphoric acid was hour. afterwhich the reaction was continued for a further 1 /2 hours to yield 205g.(97.5%) of a grey/green solid containing 2.77%P (theory 2.93%).

Timken O.K. load 60 lbs.

EXAMPLE 10 a. lsobutanol (74.0g., 1.0m.) was added dropwise to toluenedi-isocyanate 174g, 1.0m.) over 1: hour, during which time the initialtemperature of 30C. rose to C. due to the strong exotherm. The reactionwas continued, with stirring, for a further one hour.

b. To the reaction product of (a) (7l.0g., 0.5m.) was added0,0'-di-tridecyl dithiophosphoric acid (276g, 0.5m.) over A hour, anexotherm being noticed. The reaction temperature was 35C. The finalproduct was a light green liquid containing 4.72%P and 9.7%S (theory4.18% and 8.62% respectively) and was obtained in a yield of 333g.(96%).

Timken 0.K. load 45 lbs.

EXAMPLE 1 1 To the reaction product (7l.0g., 0.5m.) of Example 10(a) wasadded 0,0'-di-nonylphenyl dithiophosphoric acid (260g, 0.5m.) at 30C.over 34 hour. The reaction was continued for a further one hour at 35C.to yield 320g. (96.5%) of a yellow viscous liquid containing 4.44%P and9.6%S (theory 3.96% and 8.18% respectively).

Timken O.K. load 60 lbs.

EXAMPLE 12 EXAMPLE l3 lsobutanol l4.8g., 0.2m.) was added in bulk totoluene di-isocyanate (69.6g., 0.4m.) and reacted for one hour at30-45C. 0,0-di-2-ethylhexyl dithiophosphoric acid (76.8g., 0.2m.) wasadded dropwise over 1 hour at 30C. and reaction contined for /2 hour. To129g. of the resulting product was added. at 25C., mole equivalents ofisobutanol (12.3g.) and 0,0'-di-2- ethylhexyl dithiophosphoric acid(63.6g.) over a period of hour. After reacting for 1 /2 hours at 25C.there was obtained 201 g. of a mobile, light green liquid containing4.75%P (theory 5.15%).

EXAMPLE l4 Toluene di-isocyanate (69.6g., 04m.) and 2- ethylhexanol(26.0g., 0.2m.) were reacted for 1 hour at about 3045C.0,0'-di-2-ethylhexyl dithiophosphoric acid (76.8g., 0.2m.) was thenadded dropwise over hour at 30C. and reaction continued for 1 hour. To156g. of the resulting product were added mole equivalents of0,0'-di-2-ethylhexyl dithiophosphoric acid (67.9g.) and 2-ethylhexamol(22.4g.) and reaction continued, with stirring, for 2 hours at atemperature of 20C. There was obtained 235g, (95.4%) of a green liquidcontaining 4.15%P (theory 4.71%).

Timken O.K. load 35 lbs.

EXAMPLE l5 Toluene di-isocyanate (69.6g., 0.4m.) and isobutanol (29.6g.,0.4m.) were reacted for 2 hours, the temperature exotherming to 75c. atone stage. There was then added, at 30C. over 4 hour, 132.8g. (0.4m.) ofan 0,0'-dia1kyl dithiophosphoric acid prepared from P S and. Alfol 6(commercially available mixture of alcohols having about 6 carbonatoms). Reaction was continued, with stirring, for a further one hour toyield 215g. (92.6%) of an olive green liquid containing 5.93%? (theory5.68%).

EXAMPLE 16 Toluene di-isocyanate (69.6g., 0.4m.) and tridecanol (800g,0.4m.) were reacted together and 0,0'-di-Alfol 6 dithiophosphoric acid132.6g., 0.4m.) added over hour, with the temperature at 3035C. Thereaction was continued for a further 1 hour to yield 270g. (96%) of alight green liquid containing 4.49%P (theory 4.61%).

Timken O.K. load 50 lbs.

EXAMPLE 17 The procedure of Example 16 was repeated using toluenedi-isocyanate (69.6g., 0.4m.) and Alfol 6 (40.8g., 0.4m.) (with a strongexotherm to 80C.), and 0,0-ditridecyl dithiophosphoric acid (216g,0.4m.) to yield 32 l g. (98.5%) ofa light green viscous liquidcontaining 3.95%P (theory 4.03%).

Timken 0.14.. load 40 lbs.

EXAMPLE 18 The procedure of Example 16 was repeated using toluene(ii-isocyanate (69.6g., 0.4m.), 2-ethylhexanol (520g, 0.4m.), and0,0-di-tridecyl dithiophosphoric acid (216g, 0.4m.) to yield 327g. (98%)ofa very light green mobile liquid containing 3.74%? (theory 3.89%).

Timken O.K. load 50 lbs.

EXAMPLE 19 The procedure of Example 16 was repeated using toluenedi-isocyanate (696g, 0.4m.) 3,5,5- trimethylhexanol (57.6g., 0.4m.), and0,0-di-isobutyl dithiophosphoric acid (106.8g., 0.4m.) to yield 21 lg.(90.5%) of a light green solid containing 5.63%? (theory 5.22%).

Timken O.K. load 40 lbs.

EXAMPLE 20 isodecanol (79g, 0.5m.) was added to toluene diisocyanate(87g, 0.5m.) over A hour. The initial temperature was 50C., exothermingstrongly to a maximum 105C. The reaction mixture was cooled to 80C. andstirred for a further 1 1 hour. 0,0'-di-isobutyl dithiophosphoric acid134g., 0.5m.) was then added over A hour, keeping the temperature at7580C., and the mixture stirred for a further 14 hour, whereafterisodecanol (7.9g, was added to ensure completion of reaction. There wasobtained 201g. (96%) of a light green fairly mobile liquid containing5.3%P (theory 5.4%).

Timken O.K. load 40 lbs.

EXAMPLE 21 In a manner identical to Example 20, except that a drynitrogen stream was passed through the reaction mixture to preventmoisture absorption by toluene diisocyanate, there was prepared fromtoluene diisocyanate (435g, 2.5m.), isodecanol (395g, 2.5m.)

10 and 0,0'-di-isobutyl dithiophosphoric acid (670g, 2.5m.) a clear,light green liquid containing 5.45%! and 12.0%S (theory 5.4% and 1 1.15%respectively).

EXAMPLE 22 This was a repetition of Example 21, identical in everyrespect, and the product contained 5.3%P and 12.0%S.

Timken O.K. load 40 lbs.

EXAMPLE 23 An 0,0'-di-P1B phenyl dithiophosphoric acid was prepared fromP S and a polyisobutenyl substituted phe-' EXAMPLE 24 Phenyl isocyanate(23.8g., 0.2m.) was weighed carefully into a flask and 0,0'-di-isobutyldithiophosphoric acid (52.6g., 0.2m.) slowly added thereto. Theresulting reaction was vigorously exothermic, causing a maximumtemperature of 90C. to be obtained. Stirring was continued for hour andthe final product was a dark green liquid.

EXAMPLE 25 Toluene di-isocyanate (17.4g., 0.1m.) was placed in a flaskand 0,0'-di-isobutyl dithiophosphoric acid (268g, 0.1m.) added thereto.The reaction mixture was stirred at -80C. for 1 /2 hours and thentridecanol (20g, 0.1m.) added thereto and stirred for a further hour.The final product was a very viscous, almost colourless liquidcontaining 5.3%P (theory 5.3%).

EXAMPLES 26 TO 31 Further examples were carried out in asimilar mannerto Example 1, the relevant details of these further examples being setout in Table 1 hereinafter.

The products of various of the foregoing Examples 1 to 31 were testedfor suitability as lubricant additives, as also were five prior artadditives in accordance with US. Pat. No. 3,537,998. The prior artadditives were prepared as follows:

Additive l. [Toluene-2,4-dis-(S-carbamoyl-0,0'-di-2- hexadecyldithiophosphate Toluene di-isocyanate (17.4g., 0.1m.) was placed in aflask and 0,0'-di-hexadecyl dithiophosphoric acid (127g, 0.2m.) addedthereto, the acid being added warm from a beaker due to its waxy naturewhen cold. The addition of the dithiophosphoric acid produced anexotherm. After completion of the addition the reaction mixture washeated to 70-80C. for 2 /2 hours, to yield a cloudy, quite viscousliquid containing 4.63%P

(theory 4.66%). The product solidified after standing overnight.

Additive 2. [To1uene-2,4-di-(S-carbamoyl-0,0'-ditridecyl dithiophosphateToluene di-isocyanate (7.81 g., 0.066m.) was added dropwise to0,0-di-tridecy1 dithiophosphoric acid (44.5g., 0.09m.) at 7080C., anexotherm being noticed after each addition. Reaction was continued for Ila hours at 70-80C. to yield a very pale green liquid containing 5.35%?and 10.3%S (theory 5.34% and 11.03% respectively).

Additive 3. [To1uene-2.4-di-(S-carbamoyl-0,0'-di-pnonylphenyldithiophosphate)] 0,0-di-p-nonylphenyl dithiophosphoric acid (54.5g.,0.1m.) was added in small increments to a well-stirred solution oftoluene di-isocyanate (8.71g., 0.05m.) in benzene (65ml. The rate ofaddition was such that the resulting exotherm did not raise the reactiontemperature above 25C., the temperature being maintained below 25C.throughout. After completion of the addition the product was vacuumstripped to remove the solvent and the final product was a light greenviscous liquid containing 5.10%P and 10.16%S (theory 5.05% and 9.39%respectively).

Additive 4. [Toluene-2,4-di-(S-carbamoyl-0,0'-di-2- ethylhexyldithiophosphate)] This was prepared in a similar manner to Additive 3,from 0,0'-di-2-ethylhexyl dithiophosphoric acid (50.0g. 0.133m.) and asolution of toluene diisocyanate l l.45g., 0.066m.) in benzene (25ml)The resulting additive was a mobile. green liquid containing 6.72%P and4.48%S (theory 7.03% and 14.35% respectively).

Additive 5. [Toluene-2,4-di-(S-carbamoyl-0,0'-dioctylphenyldithiophosphate)] This additive was also prepared in a similar manner toAdditive 3, from 0,0-di-octylphenyl dithiophosphoric acid (202.4g.,0.4m.) and a solution of toluene di-isocyanate (34.8g., 0.2m.) inbenzene (80ml). The resulting additive was a viscous, light green liquidcontaining 4.70%? and 10.58%S (theory 5.23% and 10.80% respectively).

In order to evaluate the antiwear (load-carrying) properties of theadditives of the present invention the products of a number of thepreparations exemplified above were tested by means of the Timken O.K.load test in accordance with the Institute of Petroleums Test MethodIP/240/69. The apparatus employed comprises a roller mounted on aspindle, the roller being rotated against a seated metal blocklubricated with the test blend. Also mounted on the spindle is a leversystem to one end of which is applied a weight, the weight beingincreased until the test blend fails as judged by scoring of the seatedmetal block. The blends tested consisted of sufficient of the testadditives to provide a phosphorus content of 0.072% by weight in a baseoil which was 150 Solvent Neutral mineral oil having viscosities ofabout 33 and 5 cSt at 100F. and 210F. re spectively. The base oil alonehad a Timken O.K. load of 12 lbs. and the results obtained with thevarious test additives are as set out above in each relevant example.Typical results obtained in this test with the widely used zinc0.0-di-hydrocarbyl dithiophosphates, at 0.08% by weight phosphoruslevel, are 33 lbs. (hydrocarbyl mixed isobutyl and pentyl groups), 35lbs. (hydrocarbyl mixed isopropyl and capryl groups) and 12 lbs.(hyerties various blends were tested by means of the R0- tary Bomb testcarried out at 150C. and in the presence of water in the mannerdescribed in the left-hand column of page 220 of the article entitledEvaluation of Antioxidants for Automotive Lubricants Using the RotaryBomb" in the Journal of the Institute of Petroleum Vol. 55, No. 544,July 1969, Pages 219 to 226. The blends tested consisted of a base oiland sufficient of the products of the examples to provide a phosphorouscontent of 0.072% by weight, the results obtained being as follows:

Time to Induction Break Base Oil only 45 min. Base oil product ofExample 1. 122 min. Base oil product of Example 2. 78 min. Base oilproduct of Example 3. 402 min. Base oil product of Example 26. 129 min.Base oil product of Example 27. 88 min.@ Base oil Additive 4. 405 min.Base oil Additive 2. 298 min. Base oil Additive 3. 82 min.@ Base oilAdditive 5. 124 min.

500 Solvent Neutral mineral oil having viscositics of about 1 l0 and 11C51. at 100F. and 210F. respectively. em 25 p.s.i. loss.

Engine tests and tests on a Cam and Tappet machine to simulate inservice performance of blends containing the additives of the presentinvention were also carried out. The engine tests indicated that theadditives of the present invention were comparable in efficiency withthe widely used zinc 0,0'-di-hydrocarbyl dithiophosphates and goodresults were obtained on the Cam and Tappet machine.

To test Thermal Stability (deposit forming tendencies) blends of baseoil (same as in Timken O.K. load tests) containing sufficient of variousadditives to provide a phosphorus content of 0.5% by weight, were placedin pyrex test tubes (ml. of test blend in each). The test tubes werethen suspended for 1 hour in an oil bath maintained at a temperature of175 180C. so that about 1 inch of the blend was showing above thesurface of the oil bath.

Meanwhile, sintered glass crucibles had been cleaned, flushed throughwith acetone, dried in an oven at 100C. for about /2 hour, cooled in airand weighed.

After completion of the 1 hour immersion period, each blend was pouredinto approximately 200ml. of heptane and the resulting mixture filteredas quickly as possible through a crucible. The crucible contents werethen thoroughly rinsed with clean heptane to ensure all oil was removed,then dried in the oven for about /2 hour, cooled in air and re-weighed.The results obtained were expressed as the weight of precipitatecollected/weight of additive in blend X 100% In this way were evaluatedblends containing one of the aforesaid prior art additives and blendscontaining the product of Example 25, the results being as follows:

, Blends containing prior art additive 3.92%

droclrbyl g y 'p y P Blends containing Product of Example 25 0.65%

For a qualitative demonstration of antioxidant propmean valueofduplicalc was.

TABEE i EX. Dithiophosphoric Reaction Product Additional %P in Product%S in Product NO. lsocyanate Acid Temp. Notes (C.) Found Theory FoundTheory Ethyl di-p-nonylphenyl olive green lsocyanate added over 2627.6g. 206g. -s0 liquid /4 hour 5.14 5.12 10.3 10.58

TAB LE l Continued EX. Dithiophosphoric Reaction Product Additional %Pin Product 7rS in Product NO. lsocyanate Acid Temp. Notes (C.) FoundTheory Found Theory (0.4m.) (0.4m.) H 3- w W WW4 W t-Butyl di-tridccylgrey/green lsocyanate added over 27 297g. l54.8g. 80-85 liquid 1% hourand product 5.l7 523 I079 l0.80

(0.3m.) (0.3m.) reacted at 70C. for

further one hour. t-Butyl di-p-nonylphenyl yellow lsocyanate added over28 297g. l54.5g. 70-80 liquid /z hour and product 5.09 4.82 8.89 9.95

(0.3m) (0.3m.) reacted at 70C. for

further one hour. t-Octadi-tridecyl lsocyanate added over 29 decyl 2l3g.-40 i hour and reaction 3.70 3.93

ll8g. (0.4m.) continued for further (0.4m.) 1% hours with temp.

gradually returning to 20C. t-Octadi-tsobutyl lsocyanate added overdecyl 107g. 20-35 hour and reaction 5.66 5.78

l ltlg. (0.4m.) continued for further (0.4m) one hour. Small solidparticles noticed and filtered off, but further precipitate formedsubsequently and whole product eventually solidified. Allyl di-isodecyl20-45 mobile Acid added dropwise to 3| 8.3 47g. yellow liquid isocyanateat room (0.lm.) (0.lm.) temperature resulting in 6.52 6.2 13.9 l2.9

exotherrn to 45C Stirred for 2% hours We claim: 6. A compositionaccording to claim 1 containing 1. A lubricant composition consistingessentially of lubricating oil having dissolved therein from about 0.1to 10% by weight of at least one oil-soluble dithiophosphoric acidderivative having the general formula:

wherein R is selected from the group consisting of mono-valent aliphaticgroups, mono-valent aromatic groups. di-valent aliphatic groups anddi-valent aromatic groups; X is selected from the group consisting ofoxygen atoms and sulphur atoms; R is an alkyl group; R and R are thesame or different and are selected from the group consisting of alkylgroups, alkaryl groups, aryl groups, aralkyl groups and alkenyl groups;and n is 0 when R is a mono-valent group and n is I when R is a divalentgroup.

2. A composition according to claim 1 wherein R and R are selected fromthe group consisting of alkyl, alkaryl and aralkyl groups containingfrom 4 to 18 carbon atoms.

3. A composition according to claim 1 wherein R is an alkyl groupcontaining from 4 to 13 carbon atoms.

4. A composition according to claim 1 wherein R is selected from thegroup consisting of a mono-valent alkyl group containing from I to 18carbon atoms and a divalent aryl group.

5. A composition according to claim 4 wherein R is a divalent aryl groupbearing at least one alkyl substitutent and containing from 6 to 24carbon atoms.

wherein R is selected from the group consisting of mono-valent aliphaticgroups, mono-valent aromatic groups, di-valent aliphatic groups anddi-valent aromatic groups; X is selected from the group consisting ofoxygen atoms and sulphur atoms; R is an alkyl group; R and R are thesame or different and are selected from the group consisting of alkylgroups, alkaryl groups, aryl groups, aralkyl groups and alkenyl groups;and n is 0 when R is a mono-valent group and n is 1 when R is adi-valent group.

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF LUBRICATING OILHAVING DISSOLVED THEREIN FROM ABOUT 0.1 TO 10% BY WEIGHT OF AT LEAST ONEOIL-SOLUBLE DITHIOPHOSPHORIC ACID DERIVATIVE HAVING THE GENERAL FORMULA:2. A composition according to claim 1 wherein R1 and R2 are selectedfrom the group consisting of alkyl, alkaryl and aralkyl groupscontaining from 4 to 18 carbon atoms.
 3. A composition according toclaim 1 wherein R4 is an alkyl group containing from 4 to 13 carbonatoms.
 4. A composition according to claim 1 wherein R3 is selected fromthe group consisting of a mono-valent alkyl group containing from 1 to18 carbon atoms and a divalent aryl group.
 5. A composition according toclaim 4 wherein R3 is a divalent aryl group bearing at least one alkylsubstitutent and containing from 6 to 24 carbon atoms.
 6. A compositionaccording to claim 1 containing from 0.5 to 5% by weight of thedithiophosphoric acid derivatives.
 7. A composition according to claim 1containing in addition to the dithiophosphoric acid derivatives, fromabout 0.1 to 5% of a compound selected from the group consisting ofmono-octyl phenyl-Alpha -naphthylamines, mono-octyl phenyl- Beta-naphthylamines, mono-nonyl phenyl- Alpha -naphthylamines and mono-nonylphenyl-Beta -naphthylamines.
 8. An oil concentrate or additive packagecomprising from 10% to 70% by weight of a lubricating oil havingdissolved therein from 90% to 30% by weight of at least onedithiophosphoric acid derivative having the formula: